Plasma-arc furnace

ABSTRACT

A plasma-arc furnace for remelting of sheet-waste material of high reactivity metals and their alloys has a furnace chamber containing a mould, plasmatrons mounted on a roof of the chamber, and a charging device for feeding sheet-waste material into a melting zone. The charging device has a hopper arranged to contain the sheet-waste material, a water-cooled base plate, guide troughs along which the sheet-waste material is fed, and controlling means to control the feed of the sheet-waste into the melting zone. The furnace expediently employs a stripping and conveying gear to deliver remelted sheet-waste material in any desired form such as a bar or a slab.

United States Patent [191 Nautny et a].

[ PLASMA-ARC FURNACE [76] Inventors: Konstantin Troiimovich Nautny,

ultisa Krasitskogo, 17, kv. 2; Viktor Iosifovich Lakomsky, ulitsaBastionnaya, 10, kv. 30; Anatoly Ivanovich Chvertko, bulvar LasiUkrainki, 2, kv. 36, all of Kiev; Anatoly Vasilievich Zherdev, ulitsaZhdanova, 3-a; Alexandr Petrovich Voropaev, ulitsa Gorkogo, 49, kv. 71,both of Kommunarsk Voroshilovgradskoi oblasti; Viktor RomanovichPillipchuk, ulitsa Mashinostroitelnaya, 12, kv. 4, Kiev; SemenYakovlevich Shekhter, ulitsa Brestkaya, l5, kv. 18, KommunarskVoroshilovgradskoi oblasti; Alexandr Mikhailovich Reznitsky, ulitsaKirova, 2, kv. 18, Kommunarsk Voroshilovgradskoi oblasti; LeonidNikolaevich Tsipura, ulitsa Gagarina, 23, kv. 24, KommunarskVoroshilovgradskoi oblasti; Oleg Semenovich Zabarilo, ulitsa Chapaeva,2/10, kv. 3, Kiev, all of USSR.

[22] Filed: Oct. 1, 1971 [21] Appl. No.1 186,267

Oct. 1, 1970 [52] US. Cl 13/33, 13/9, 214/23 [5l] Int. Cl H051) 7/00,F27d 3/00 [58] Field of Search 13/]. 9, 33, 31;

Primary ExaminerRoy N. Envall, .l r. AttorneyHolman & Stern [5 7ABSTRACT A plasma-arc furnace for remelting of sheet-waste material ofhigh reactivity metals and their alloys has a furnace chamber containinga mould, plasmatrons mounted on a roof of the chamber, and a chargingdevice for feeding sheet-waste material into a melting zone. Thecharging device has a hopper arranged to contain the sheet-wastematerial, a water-cooled base plate, guide troughs along which thesheet-waste material is fed, and controlling means to control the feedof the sheet-waste into the melting zone. The furnace expedientlyemploys a stripping and conveying gear to deliver remelted sheet-wastematerial in any desired from such as a bar or slab.

4 Claims, 5 Drawing Figures SHEET 2 BF 4 PATENTED DEC 4 I975 PLASMA-ARCFURNACE BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to electrometallurgy and more particularly todevices for plasma-arc remelting of wastes produced in sheet rollinghigh-reactivity metals (titanium, zirconium, etc.) and their alloys.

2. Description of Prior Art Widely known are plasma-arc furnaces for theremelting of a consumable blank, comprising a chamber with a blank feedgear, fitted with plasmatrons, and a mould butting against said chamber.

The use of these furnaces for the production of slabs (ingots) ofhigh-reactivity metals and their alloys from their wastes necessitatesfor the manufacture of a consumable electrode a double remelting processsince single melting does not ensure the requisite quality of blanksurface.

Consumable electrodes for plasma-arc furnaces can be manufactured eitherfrom sheet wastes of highreactivity metals and alloys or from a majorcharge component (sponge) to which said wastes are added.

For producing the electrodes from the sheet wastes diversified methodscan be utilized, such as for exam ple, pressing, welding, joining sheetwastes together by means of special fittings, etc.

In order to convey the electrodes manufactured using the wastes by theaforesaid procedures into the remelting zone, use is made of furnaceshaving feed gears, providing with both vertical movement and rotation(oscillation).

However, peculiar to the furnaces equipped with such gears is asophisticated construction. As for the manufacture of electrodes fromrolled sheet wastes, it necessitates intricate production equipment. Allthis is labour-consuming, and is associated with large expediture andlow production rate; in some cases, particularly in producing heavyingots, the above technique is not suitable at all for the fabricationof electrodes. It restricts potential uses of sheet wastes formanufacturing ingots of the requisite dimensions and cross-section.

SUMMARY OF THE INVENTION It is an object of the present invention toincrease the efficiency of a waste-remelting furnace by charging it withrolled sheet wastes cut in specified lengths. Another object of thisinvention is to reduce both the process labour input and expenditure onpreparation of consumable electrodes for remelting. Still another objectof the invention is to simplify the furnace construction and to ensurethe melting in this furnace of the ingots of the requisite size andweight.

According to the specified and other objects in a plasma-arc furnace forremelting sheet-wastes of highreactivity metals incorporating a chamberwith a charging device and plasmatrons mounted in its roof, and a mouldbutting against the lower part of said chamber, conforming to theinvention, the charging device has an air-tight hopper arranged in theupper part of the chamber together with a sheet-waste container, awater-cooled base-plate with guide troughs set up between the containerand the mould and a gear located under the container and intended forfeeding sheetwastes along the troughs of the said baseplate into theremelting zone which will permit reducing. time and labour requirementsfor the remelting of sheet trimmings.

The'sheet-waste feed gear has a mobile carriage including pushers andsaid container hinged thereto and further comprising severalcompartments slotted in their lower portion to let said pushers pass.Provided in the lower portion of the container front wall are ports withslides-uncovering to pass sheet-wastes. With the above construction theremelting of sheet-wastes can be accomplished without packing them intoelectrodes thus simplifying substantially the production process.

The furnace can be equipped with at least two identical charging devicesset up around the mould which enables sheet-wastes to be fed into theremelting zone in several flows at one and the same time.

All the gears and assemblies of the charging device are mounted in thefurnace in succession ensuring a continuous technological process offeeding the wastes, cut in specified lengths, into the remelting zonewith the ensuing production at the end of this process of ingots havingthe requisite weight.

BRIEF DESCRIPTION OF THE DRAWINGS Described below is an exemplaryembodiment of the invention to be considered with reference to theaccompanying drawings, in which:

FIG. 1 is a fragmentary longitudinal sectional view of a plasma-arcfurnace, conforming to the invention;

FIG. 2 shows a general view (with a fragmentary cutaway) of a furnacecontainer of the plasma-arc furnace of FIG. 1;

FIG. 3 section II-II of FIG. 1;

FIG. 4 section III-III of FIG. 1;

FIG. 5 section IV--IV of FIG. 2.

A plasma-arc furnace has a welded flat box-type chamber 1 (FIG. 1) whichserves for erecting main asse'mblies. The chamber 1 has in its mediumportion a through opening (not shown in the drawing) above which acollapsable roof (not shown in the drawing) is placed. The roof is madein the form of a rectangular box enclosed in a water jacket extendingthroughout its surface. The upper portion of the roof is fitted withholes through which pass plasmatrons 2 arranged so that they are free tomove vertically and radially. The furnace roof is hinged to chamber 1.Fastened on the opposite side of the hinged portion of the roof are tworollers through which passes a rope associated with a roof lifting gear.Under the roof secured to the base of chamber 1 is a casing constitutinga mould 3. The casing of mould 3 is a welded rectangular constructionopen at the top. At its bottom there are: a rectangular opening toreceive an ingot, a dummy bar of an ingot withdrawing device (not shownin the drawing) and six circular holes through which run pipes forcooling the mould 3'. The entire surface of the casing of mould 3 isenclosed in the a water jacket and the upper part of the casing isfitted with a flange (not shown in the drawing) intended for bolting thecasing of mould 3 to the furnace chamber 1; Mould 3 is mounted oninternal projecting parts of the flange being separated from it by meansof insulating straps. Located below the casing of mould 3 along itsperimeter are special grippers (not shown inthe drawing) through whichit is coupled to the ingot withdrawing device. Mould 3 is of a compositecopper-steel construction with water cooling. Water is supplied anddischarged via six copper pipes passing through the holes in the bottomof the casing of mould 3.

Chamber 1 is equipped with two charging devices (not shown in thedrawing) located symmetrically relative to mould 3.

Each charging device comprises a hopper 4 which serves for accommodatingcontainer 5.

Each of the two hoppers 4 is made in the form of a hollow box flanged atthe top and underneath and open at both ends. The lower flange of eachhopper 4 is secured at the top of chamber 1 under a hole for container Sby means of a hermetic connection, while the upper flange carriesswivelling cover 6 hinged to it. Lateral faces of both hoppers 4 haveflanges in their upper portions whose purpose is to couple piping of agas circulating and recovery system. In addition oneof the hoppers 4 isfitted with a safety valve which connects the furnace interior withatmosphere and cuts off all feed sources if pressure within the furnacebuilds up.

The container serves for accommodating wastes 7 and loading them intothe furnace for remelting. Container 5 comprises housing 8 (FIG. 2)subdivided into several compartments 9 in which is placed sheet-waste 7cut in specified lengths and piled to be remelted. The bottom of eachcompartment 9 has longitudinal through slots 10 located centrally. Thelower portion of the front wall of container 5 is fitted with portsthrough which the sheet-waste 7 to be remelted pass into the remeltingzone. Guides 11 cater for positioning container 5 in chambr l of thefurnace.

Two eyebolts 12 are employed for handling container 5 with the aid ofhoisting gears (not shown in the drawing), the eye bolts beingsecured'to an upper partition of container 5 from above.

Disposed between container 5 and mould 3 is watercooled base-plate 13.

Base-plate 13 is of welded construction is made up of copper sheets; itis intended to direct sheet-waste 7 to be remelted ontheir way fromcontainer 5 to the melting zone. Its upper portion is provided withguide troughs 14 whose number depends on the number of compartments 9 ofcontainer 5. The base plate is fastened to chamber 1 in a horizontalposition.

Located under container 5 in the furnace chamber 1 is gear 15 forpushing sheet-wastes 7 one after another from container 5 and feedingthem along guide troughs 14 into the melting zone.

Sheet-waste feed gear 15 comprises a carriage 16 whose upper portion isfitted with a nut 17 which has a through hole extending over its lengthand intended for a drive screw 18; four rollers 19 with shaped grooves,are secured in bearing assemblies on either side along carriage 16 onshafts 20 (FIG. 3) and are coupled thereto by means of a rigid joint;two guide rods 21 are fastened on brackets 22 (FIG. 4) of chamber l withthe internal sides of the rods having doublesided bevels extending alongtheir length and receiving the shaped grooves of rollers 19', pushers 23are provided whose height is adjusted by replaceable carns attached inthe front portion of carriage 16 on pivots 24 the pushers being free torotate on the pivots (the rear part of the pushers is chamfered);springs 25 (two per each pusher) are provided forcing pushers 23 againstresets 26 (one end of springs 25 is inserted into the apertures inpushers 23 and their other end in the openings in screw 27 driven intocarriage 16); a drive screw 18 is driven in nut 17 with the screw frontend fastened in a bearing block mounted in stand 28 connected by meansof a rigid joint to the bottom of chamber 1 with the other end securedin a bearing block arranged in cover 29 which is attached to the rearwall of chamber 1. Screw 18 projects through vacuum seal 30 and its tailcarries a rigidly fitted gear wheel 31 through which feeding gear 15 iscoupled to drive 32.

Drive 32 serves for imparting to the pushers 23, a translatory motionwith a requisite speed in the direction of base-plate l3 and returns thepushers with a high speed into an initial extreme rear position. Drive32 is attahced to the exterior of chamber 1 above sheetwaste feedinggear 15. v

Fastened by bolts 33, to the front wall of container 5 near the wasteoutlet (FIG. 5) is a slide 34 shifted verticallyby means of a specialbolt 35.

The purpose of slide 34 is to restrict the amount of sheet-wastematerial supplied from container 5 and delivered by pushers 23 into theremelting zone.

The number of pushers 23 in sheet-waste feeding gear 15, and the numberof compartments 9 in container 5 and troughs 14in base-plate 13 areaccordingly equal. The spacings between the axes of symmetry of theseelements are also equal.

The furnace is fitted with a discharge gear (not shown in the drawing)intended for withdrawing an ingot from mould 3 and conveying it to astorage. The discharge gear is made up of: an ingot withdrawing gear,power feeders, a frame and a car (not shown in the drawing).

The furnace feeders can be made in the form of brushes mounted on theingot withdrawing gear.

The discharge gear frame is arranged on a car. It can be made in theform of a truncated cone, made from angles with flat sides from aboveand underneath having rectangular holes through which the ingotwithdrawing gear passes. The car moves on a rail track and has mountedthereon all the assemblies of the discharge gear, a hydraulic cabinetand a pumping plant. The car is also intended for conveying the meltedingot to the storage.

Incorporated in the furnace is also a gear (not shown in the drawing)for roof lifting for cleaning and for inspecting base-plate 13 and mould3.

For cooling the furnace assemblies, arranged to cool the hightemperature zone is provided a cooling system which consists of ahydraulic unit, a pumping plant, elements for distributing water amongthe units to be cooled, a reservoir and water flow and temperaturecontrols. The furnace components to be cooled are subdivided into twogroups: those cooled by conventional water flow and those cooled bycomparitively soft water which does not produce scale. Soft water isused for cooling mould 3, the dummy bar (not shown in the drawing) andplasmatrons 2. Flow relays are set up at the conduit outlet of all thesecomponent cooling assemblies. In addition, each conduit is controlled bya temperature relay. The furnace is equipped with a hydraulic systemwhose purpose is to tighten and to secure the ingot withdrawing gear tothe casing of mould 3 prior to melting as well as to displace the ingotdischarge gear (not shown in the drawing) to the discharge and returnto'its initial position under mould 3.

For feeding plasmatrons 2 the furnace has a gas recovery and circulationsystem.

The. furnace operates in the following manner.

In the initial position container 5 (FIG. 1) accommodating piled wastesto be remelted is placed in hopper 4. Its lower part passes through theopening in chamber 1. Container 5 rests on stand 36 welded to the wallsof chamber 1.

The upper edge of the bottom of container 5 on which sheet-wastes 7 tobe remelted are lying rises slightly above the bottom of troughs 14 ofbase-plate 13. Pushers 23 with carriage 16 are set up in the extremerear position and are drawn out of slots (FIG. 2) provided in the bottomof compartments 9 of container 5. As pushers 23 advance forward theirheight provides for gripping and ejecting from container 5 the requisiteamount of sheet-waste 7 to be remelted.

Slide 34 (FIG. 5) is arranged at a level ensuring free passage ofmaterial 7 (to be remelted), pulled by pushers 23 from container 5,through the ports in the front wall of container 5.

In the initial position the axes of symmetry of pushers 23, compartments9 and troughs 14 of base-plate 13 are made to coincide.

When in the initial position the dummy bar (not shown in the drawing) isinserted into the interior of mould 3 up to its upper chamfered region.

The furnace roof (not shown in the drawing) is lowered. Next the gasrecovery and circulation system is turned on. The requisite pressure ismaintained in the chamber 1 of the furnace. Supply sources are coupledto the ingot withdrawing gear. Then the water cooling system is cut inand all plasmatrons 2 of the furnace are actuated alternately toaccomplish the remelting process. The unit is started by bringing aglowing torch near to the metal charge in mould 3 whereupon the systemoperates for returning plasmatrons 2 into initial operating position.

For feeding the sheet-waste to be remelted into the remelting zone,drive 32 whose shaft is automatically reversed after the requisitenumber of revolutions, imparts a reciprocating motion to pushers 23fastened on carriage 16 (FIGS. 3 and 4) of sheet waste feeding gear viagear train 31, drive screw 18 and nut 17. The rate at which pushers 23move forward (operating speed) can be adjusted within a wide range, withthat of the reverse motion (operating speed) being constant and maximum.

As pushers 23 move forward from their extreme rear position, they enterthrough slots 10 provided in the bottom of compartments 9 of container 5(with the direction of movement of the pushers coinciding with that ofslots 10 in compartments 9), approach the lower strips of the material 7to be melted, and striking against their butt ends eject them throughthe ports in the front wall of container 5 into troughs 14 in baseplate13 and then into the remelting zone.

Molten material from the blanks being fused flows into mould 3 and theingot being performed is drawn out by the withdrawing gear. The numberof the waste strips pushed out of container 5 is controlled by slide 34.When the lower strips are pushed out, the upper ones descend by gravityto take their place and pushers 23 coming out of the limits of container5 reach their extreme front position.

As pushers 23 (FIG. 3) move from the extreme front into rear positiontheir chamfers run into wastes 7 lying in container 5, revolve aboutpivots 24 in an opposite direction relative to the movement of carriage16, expanding springs 25, which force them against rests 26 and ensuringthereby slippage of pushers 23 with regard to wastes 7 being remelted.On coming out of contact with the sheet-waste, pushers 23 return intotheir initial position under the action of springs 25 and lean againstrests 26. The cycle described above is reiterated.

The plasma-arc furnace, proposed herewith, allows remelting sheet-wastesof high-reactivity metals and alloys to produce from them directly slabsof any desired section and a high quality, thereby providing for areduction in time and labour requirements when rolling slabs intosheets, the invention also ensures an increase in the yield of rolledproducts and reduces the cost of rolled sheets.

What is claimed is:

l. A plasma-arc furnace for the remelting of sheetwaste material ofhigh-reactivity metals and their alloys, comprising: a chamber forremelting the said sheet-waste material, said chamber having a roof anda melting zone; plasmatrons mounted on the roof of the said chamber; amould means disposed in a lower part of the said chamber and designedfor forming an ingot out of molten sheet-waste material; at least onecharging device enclosed in the said chamber and including: an air-tighthopper having a container to accommodate said sheet-waste materialarranged in an upper portion of the said chamber, a water-cooledbase-plate having guide troughs mounted between the said container andthe mould, and means for feeding said sheet-waste material along theguide troughs of the said base-plate into said melting zone, said meansfor feeding being located in said chamber substantially under saidcontainer.

2. A plasma-arc furnace as claimed in Claim 1, in which said means forfeeding includes a carriage having pusher means for pushing thesheet-waste material.

3. A plasma-arc furnace as claimed in claim 2, in which the saidcontainer has a front wall, and compartments whose lower part isprovided with longitudinal through slots formed to let pass said pushersand wherein in a lower part of the front wall of said container thereare ports with slides uncovering to let said sheet-waste pass through.

4. A plasma-arc furnace of as claimed in Claim 1 in which at least twoidentical charging devices located around said mould are provided.

1. A plasma-arc furnace for the remelting of sheet-waste material ofhigh-reactivity metals and their alloys, comprising: a chamber forremelting the said sheet-waste material, said chamber having a roof anda melting zone; plasmatrons mounted on the roof of the said chamber; amould means disposed in a lower part of the said chamber and designedfor forming an ingot out of molten sheet-waste material; at least onecharging device enclosed in the said chamber and including: an air-tighthopper having a container to accommodate said Sheet-waste materialarranged in an upper portion of the said chamber, a water-cooledbase-plate having guide troughs mounted between the said container andthe mould, and means for feeding said sheet-waste material along theguide troughs of the said base-plate into said melting zone, said meansfor feeding being located in said chamber substantially under saidcontainer.
 2. A plasma-arc furnace as claimed in Claim 1, in which saidmeans for feeding includes a carriage having pusher means for pushingthe sheet-waste material.
 3. A plasma-arc furnace as claimed in claim 2,in which the said container has a front wall, and compartments whoselower part is provided with longitudinal through slots formed to letpass said pushers and wherein in a lower part of the front wall of saidcontainer there are ports with slides uncovering to let said sheet-wastepass through.
 4. A plasma-arc furnace of as claimed in Claim 1 in whichat least two identical charging devices located around said mould areprovided.